PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 10 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Tissue PART 1

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle  Muscle – a Latin word for “little mouse”  Muscle is the primary tissue in the  Heart (cardiac MT)  Walls of hollow organs (Smooth MT)  Skeletal muscle  Makes up nearly half the body’s mass

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Muscle Tissue  Functions of muscle tissue  Movement  Skeletal muscle - attached to skeleton  Moves body by moving the bones  Smooth muscle – squeezes fluids and other substances through hollow organs

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Muscle Tissue  Functions of muscle tissue (continued)  Maintenance of posture – enables the body to remain sitting or standing  Joint stabilization  Heat generation  Muscle contractions produce heat  Helps maintain normal body temperature

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Functional Features of Muscles  Functional features  Contractility  Long cells shorten and generate pulling force  Excitability  Electrical nerve impulse stimulates the muscle cell to contract

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Functional Feature of Muscles  Functional features  Extensibility  Can be stretched back to its original length by contraction of an opposing muscle  Elasticity  Can recoil after being stretched

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Types of Muscle Tissue  Three types of MT  Skeletal muscle tissue  Packaged into skeletal muscles  Makes up 40% of body weight  Cells are striated

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Types of Muscle Tissue  Three types of MT (continued)  Cardiac muscle tissue – occurs only in the walls of the heart  Smooth muscle tissue – occupies the walls of hollow organs  Cells lack striations

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Similarities of Muscle Tissue  Cells of muscles  Are known as fibers  Muscle contraction  Depends on two types of myofilaments (contractile proteins)  One type contains actin  Another type contains myosin  These two proteins generate contractile force

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Similarities of Muscle Tissues  Plasma membrane is called a sarcolemma  Cytoplasm is called sarcoplasm

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle  Each muscle is an organ  Consists mostly of muscle tissue  Skeletal muscle also contains  Connective tissue  Blood vessels  Nerves

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Basic Features of a Skeletal Muscle  Connective tissue and fascicles  Connective tissue sheaths bind a skeletal muscle and its fibers together  Epimysium – dense regular connective tissue surrounding entire muscle  Perimysium – surrounds each fascicle (group of muscle fibers)  Endomysium – a fine sheath of connective tissue wrapping each muscle cell

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Basic Features of a Skeletal Muscle  Connective tissue sheaths are continuous with tendons  See Figure 10.1a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Connective Tissue Sheaths in Skeletal Muscle Figure 10.1a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Basic Features of a Skeletal Muscle  Nerves and blood vessels  Each skeletal muscle supplied by branches of  One nerve  One artery  One or more veins

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Basic Features of a Skeletal Muscle  Nerves and blood vessels  Nerves and vessels branch repeatedly  Smallest nerve branches serve  Individual muscle fibers  Neuromuscular junction – signals the muscle to contract  Draw a picture of neuromuscular junction

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Basic Features of a Skeletal Muscle  Muscle attachments  Most skeletal muscles run from one bone to another  One bone will move – other bone remains fixed  Origin – less movable attachment  Insertion – more movable attachment

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Attachments Figure 10.3

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Basic Features of a Skeletal Muscle  Muscle attachments (continued)  Muscles attach to origins and insertions by CT  Fleshy attachments – CT fibers are short  Indirect attachments – CT forms a tendon or aponeurosis  Bone markings present where tendons meet bones  Tubercles, trochanters, and crests

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic and Functional Anatomy of Skeletal Muscle Tissue  The skeletal muscle fiber  Fibers are long and cylindrical  Are huge cells – diameter is 10–100µm  Length – several centimeters to dozens of centimeters  Each cell formed by fusion of embryonic cells  Cells are multinucleate  Nuclei are peripherally located

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Diagram of Part of a Muscle Fiber Figure 10.4b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Myofibrils and Sarcomeres  Striations result from internal structure of myofibrils  Myofibrils  Long rods within cytoplasm  Make up 80% of the cytoplasm  Are a specialized contractile organelle found in muscle tissue  A long row of repeating segments called sarcomeres (functional unit of Skeletal MT)

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcomere  Basic unit of contraction of skeletal muscle  Z disc (Z line) – boundaries of each sarcomere  Thin (actin) filaments – extend from Z disc toward the center of the sarcomere  Thick (myosin) filaments – located in the center of the sarcomere  Overlap inner ends of the thin filaments  Contain ATPase enzymes

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcomere Structure  A bands – full length of the thick filament  Includes inner end of thin filaments  H zone – center part of A band where no thin filaments occur

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcomere Structure (continued)  M line – in center of H zone  Contains tiny rods that hold thick filaments together  I band – region with only thin filaments  Lies within two adjacent sarcomeres

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcoplasmic Reticulum and T Tubules  Sarcoplasmic reticulum  A specialized smooth ER  Interconnecting tubules surround each myofibril  Some tubules form cross-channels called terminal cisternae  Cisternae occur in pairs on either side of a t-tubule

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcoplasmic Reticulum and T Tubules  Sarcoplasmic reticulum  Contains calcium ions – released when muscle is stimulated to contract  Calcium ions diffuse through cytoplasm  Trigger the sliding filament mechanism

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcoplasmic Reticulum and T Tubules in the Skeletal Muscle Fiber Figure 10.6

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcomere and Myofibrils Figure 10.4c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Contraction  Sliding filament theory  Myosin heads attach to actin in the thin filaments  Then pivot to pull thin filaments inward toward the center of the sarcomere PLAY Sliding Filament Theory

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sliding Filament Mechanism Figure 10.7a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Changes in Striation During Contraction Figure 10.8a–c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic and Functional Anatomy of Skeletal Muscle Tissue  Muscle extension  Muscle is stretched by a movement opposite that which contracts it  Muscle fiber length and force of contraction  Greatest force produced when a fiber starts out slightly stretched  Myosin heads can pull along the entire length of the thin filaments

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Role of Titin  Titin – a spring-like molecule in sarcomeres  Resists overstretching  Holds thick filaments in place  Unfolds when muscle is stretched Figure 10.4d

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Sarcoplasmic Reticulum and T Tubules  Muscle contraction  Ultimately controlled by nerve-generated impulse  Impulse travels along the sarcolemma of the muscle cell  Impulses further conducted by T tubules  T tubule – a deep invagination of the sarcolemma PLAY Anatomy Review: Skeletal Muscle Tissue

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Skeletal Muscle  Motor neurons innervate skeletal muscle tissue  Neuromuscular junction is the point where nerve ending and muscle fiber meet

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Skeletal Muscle Figure 10.9

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Skeletal Muscle Figure 10.10